Microcontrollers and Embedded Systems
Core concepts
Understand microcontroller architecture: CPU core, memory map (flash, RAM, EEPROM), peripherals, buses, and clock sources. Know the difference between Harvard and von Neumann architectures, and between polling, interrupts and DMA. Candidates must grasp GPIO configuration, timers and counters, PWM generation, ADC and DAC peripherals, and serial interfaces such as UART, SPI and I²C, including their typical speeds and wiring. Familiarity with embedded C concepts-volatile variables, bit masking, register access-and with real-time constraints, watchdog timers and low-power modes is expected. Basic understanding of firmware development flow (compile, link, flash, debug) is also required.
Traps
Questions often confuse SPI (four-wire, full-duplex, master-controlled clock) with I²C (two-wire, addressed, open-drain with pull-ups). Another trap is forgetting that interrupt service routines should be short and that shared variables need volatile or atomic handling. Watch for stack versus heap confusion and for the difference between a timer's prescaler and period. Reading a datasheet register bit position incorrectly is a common practical error.
Worked example
A 16 MHz timer with prescaler 64 and period register 249 overflows every (64 × 250)/16 MHz = 1 ms. Rule of thumb: timer interval = prescaler × (period + 1) / clock frequency; always add one to the period because counting starts at zero.